"activity that seems to indicate malware."
Adware is not malware - by definition, so actually nothing in your stats indicates malware.
"The first entry in the screenshot, ib.adnxs.com, which has appeared the most, I thought was potential malware, from Google searching that url."
Google doesn't know, and the sources may not really be reliable. Most of them are simple internet visitors, not really skilled and experienced.
And because the domain is blocked for you, you could not have been able to download any malware (or even adware) from them, so no reason to be worried. As I said, you already get what you want, and you are protected.
"The activity isn't from normal web browsing, assuming the dates and time stamps are correct. I can confirm no one was accessing the web at the time."
These domains definitely come from normal web browsing, as I know from much experience with OpenDNS stats. And if you think nobody was browsing at this time, you first should check the time zone for your account to possibly correct it:
https://dashboard.opendns.com/myaccount/timezone
If it was correct, then someone else may have accessed your LAN, e.g. through an unprotected WLAN AP and the likes.
"Is it possible that malware of some sort can hijack and forward requests to specific sites?"
What? No! This is not what would make sense. DNS queries are never ever forwarded to "specific sites", whatever this could mean. However, malware could raise DNS look-ups with the intent to phone home to download even more malware or to transmit internal information to the outside world. But as I said, absolutely nothing indicates such behavior in your stats.
